Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
Ho there. I am Cam.Do you have anything aftermarket wired in?
Ok, this may just be a sticking relay. Try tapping on the relays in the fuse block under the hood with the engine running and key off. If tapping makes it stop. replace that relay. If this doe snot change it, then we need to start looking for water intrusion in the fuse blocks, chaffed wiring and such as well. Its likely just a wire touching somewhere. Normally the issue is in the fuse block under the dash by the drivers left foot. A common point to add wiring for ignition and battery are side by side, but the terminals often touch and cause this.
Check wiring on the end dash fuse block as well please.
You will need to start pulling fuses to see which makes it stop. That will help narrow down what circuit is causing this issue.
Many of the codes will be set because of the BCM not being programmed to your vehicle.
The ECU is not shutting off, we know that. The issue is one of the power feeds normally meant for ignition power is getting battery power, through either a shorted wire directly to that, or possibly the ground control for the relays grounded. At this exact moment I don't know where the issue is, I would need to do more diagnosis to find it which I am trying to get you to do. Pulling fuses will help narrow down which circuit is the issue. There may be more than one.